Sheet mulching is a technique for creating a garden bed that does not require tilling or hand weeding. It is intended to mimic the natural mulching process that occurs on the forest floor. It is also suitable for converting a section of lawn into a garden without breaking the sod. There are a lot of different methods but here is the simplest one:

Trample or cut down any large woody weeds.

Put down a layer of compost to jump-start the composting process.

Create a thick weed-barrier of newspaper, cardboard, or other biodegradable materials over the area you want to convert, wetting with a hose as you go.

The top layer mimics the materials that fall to forest floor - nut shells, twigs, fern fronds, coffee grounds, wood chips, etc. are all good materials. Create a layer 3-5 inches thick and water in.

Plants can be transplanted directly into this bed and should be closely spaced to minimize the germination of weeds. Note: this method is not recommended for areas that are prone to flooding or waterlogging.
Graphic courtesy of agroforestry.net